When Two Liquid Droplets Become One Together

One of the many entertaining things I found as a child was to watch rain droplets roll down a window when it’s raining. It also is satisfying to watch two tiny droplets become a little bit bigger when they merge into one. Scientists just did the latter in a lab, and it became more satisfying to see.

Two synchronized cameras, shooting up to 25,000 frames a second, recorded different angles of the droplet interaction. As one dyed droplet was dripped from a pump, landing next to a clear droplet sitting on a slide, both a side-on and underneath view allowed researchers to study both surface and internal changes to the droplets.

“In the past, there have been instances when two droplets impact and you were left wondering whether they have mixed or has one droplet just passed over the other,” Dr Alfonso Castrejón-Pita, an associate professor and co-author of the study, based at the University of Oxford, said in a statement. “Having two cameras record the droplet interaction from different viewpoints answers that question.”

Breathtaking.

(Image Credit: University of Leeds)